NorthStar 2201, Installation Manual

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Glossary and acronyms
2201 INSTALLATION MANUAL, Revision B Page 45
MSK Minimum Shift Keying (the type of modulation used by the
BDM, about 50 Hz shift).
NMEA National Marine Electronics Association: The industry group
that has established standards for exchanging data between
electronic navigation equipment. “NMEA 0183” is the standard
that’s now widely in use. It specifies the format for “sentences”
containing specific types of data.
NVM Non-Volatile Memory.
PAL Programmed Array Logic chip.
PRN Pseudo Random Number (satellite ID number).
RAM Random Access Memory.
RF Radio Frequency.
RMS Root Mean Square. In positioning accuracy, these units reflect
that approximately 66 percent of positions are within the
quoted, e.g., 1m RMS.
2dRMS is a 95 percent accuracy figure, e.g., <3m 2dRMS, and is
the preferred term for navigation accuracy.
RTCM Radio Technical Commission for Maritime Services, for
standards and performance minimums.
satellite An object orbiting the earth. GPS satellites are controlled by
ground stations, and transmit signals that can be used to
calculate position and speed.
SC-104 The digital communication specification for the differential
corrections format.
sentence A group of data in one of several formats defined by the
National Marine Electronics Association. For standard
applications, the 2201/NMEA is programmed to output the
necesssary sentences.
TDOP Time Dilution of Precision.
TTFF Time To First Fix.